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Single Packet Authorization (SPA). fwknop stands for the "FireWall KNock OPerator", and implements an authorization scheme called Single Packet Authorization (SPA). This method of authorization is based around a default-drop packet filter (fwknop supports both iptables on Linux systems and ipfw on FreeBSD and Mac OS X systems) and libpcap. SPA requires only a single encrypted packet in order to communicate various pieces of information including desired access through an iptables policy and/or complete commands to execute on the target system. By using iptables to maintain a "default drop" stance, the main application of this program is to protect services such as OpenSSH with an additional layer of security in order to make the exploitation of vulnerabilities (both 0-day and unpatched code) much more difficult. With fwknop deployed, anyone using nmap to look for sshd can't even tell that it is listening; it makes no difference if they have a 0-day exploit or not. The authorization server passively monitors authorization packets via libcap and hence there is no "server" to which to connect in the traditional sense. Access to a protected service is only granted after a valid encrypted and non-replayed packet is monitored from an fwknop client (see the following network diagram; the SSH session can only take place after the SPA packet is monitored): PR: ports/118229 Submitted by: Sean Greven <sean.greven@gmail.com>
113 lines
4.2 KiB
Groff
113 lines
4.2 KiB
Groff
--- fwknopd.8.orig 2007-11-21 20:59:13.000000000 +0200
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+++ fwknopd.8 2007-11-21 21:02:20.000000000 +0200
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@@ -26,7 +26,7 @@
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and
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.B access.conf
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within the
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-.B /etc/fwknop
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+.B %%PREFIX%%/etc/fwknop
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directory, and configuration variables within these files are desribed below.
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.SH OPTIONS
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.TP
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@@ -34,7 +34,7 @@
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When run in server mode
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.B fwknop
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references the file
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-.B /etc/fwknop/fwknop.conf
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+.B %%PREFIX%%/etc/fwknop/fwknop.conf
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for various run-time configuration
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variables. The path to this file can be changed through the use of the
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.B --config
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@@ -42,7 +42,7 @@
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.TP
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.BR \-i "\fR,\fP " \-\^\-intf\ \<interface>
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Manually specify interface on which to sniff, e.g. "-i eth0". This option
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-is not usually needed because the PCAP_INTF keyword in /etc/fwknop/fwknop.conf
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+is not usually needed because the PCAP_INTF keyword in %%PREFIX%%/etc/fwknop/fwknop.conf
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file defines the sniffing interface.
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.TP
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.BR \-\^\-fw-list
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@@ -80,32 +80,32 @@
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.BR \-V "\fR,\fP " \-\^\-Version
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Display version information and exit.
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.SH FILES
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-.B /etc/fwknop/fwknop.conf
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+.B %%PREFIX%%/etc/fwknop/fwknop.conf
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.RS
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The main configuration file for
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.B fwknop.
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.RE
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-.B /etc/fwknop/access.conf
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+.B %%PREFIX%%/etc/fwknop/access.conf
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.RS
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Defines all knock sequences and access control directives.
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.RE
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-.B /etc/fwknop/pf.os
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+.B %%PREFIX%%/etc/fwknop/pf.os
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.RS
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Defines p0f signatures used by fwknop.
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.RE
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.SH FWKNOP CONFIG AND ACCESS VARIABLES
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.B fwknop
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references the file
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-.B /etc/fwknop/fwknop.conf
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+.B %%PREFIX%%/etc/fwknop/fwknop.conf
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for configuration variables such as the path to the firewall logfile,
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the sleep interval fwknop uses to check for new log messages, and
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paths to system binaries, etc. The
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.B fwknop
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config file does not define any access control directives; they are
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located in the file
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-.B /etc/fwknop/access.conf.
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+.B %%PREFIX%%/etc/fwknop/access.conf.
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Access control directives define encryption keys and level of access that
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is granted to an fwknop client that has generated the appropriate encrypted
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message. This file is referenced for this information when run in either
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@@ -116,7 +116,7 @@
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legacy knock sequence) will be accepted. The string "ANY" is also
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accepted if a valid authorization packet should be honored from any source
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IP. Every authorization stanza in
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-.B /etc/fwknop/access.conf
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+.B %%PREFIX%%/etc/fwknop/access.conf
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definition must start with the SOURCE keyword. Networks can be
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specified in either CIDR (e.g. "192.168.10.0/24") or regular (e.g.
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"192.168.10.0/255.255.255.0") notation, and individual IP addresses
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@@ -178,7 +178,7 @@
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on the client, but each fwknopd server should have its own gpg key that is
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generated specifically for fwknop communications. The reason for this is
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that the decryption password for the server key must be placed within the
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-.B /etc/fwknop/access.conf
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+.B %%PREFIX%%/etc/fwknop/access.conf
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file for fwknopd to function (it has to be able to decrypt SPA messages that
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have been encrypted with the server's public key). For more information on
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using fwknop with GnuPG keys, see the following link:
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@@ -204,7 +204,7 @@
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Define the path to the GnuPG directory to be used by the
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.B fwknopd
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server. If this keyword is not specified within
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-.B /etc/fwknop/access.conf
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+.B %%PREFIX%%/etc/fwknop/access.conf
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then fwknopd will default to using the /root/.gnupg directory for the server key(s).
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.TP
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.B FW_ACCESS_TIMEOUT: <seconds>
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@@ -235,7 +235,7 @@
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"Linux:2.4::Linux 2.4/2.6" or "OpenBSD:3.0-3.5::OpenBSD 3.0-3.5"
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before a knock sequence will be accepted. The fingerprints are listed
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in
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-.B /etc/fwknop/pf.os.
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+.B %%PREFIX%%/etc/fwknop/pf.os.
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Note that the corresponding knock sequence must utilize the tcp protocol
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(this is only be an issue for shared sequences since encrypted sequences
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use tcp by default) since OS fingerprinting requires tcp syn packets.
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@@ -281,7 +281,7 @@
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starting at a default port of 61000. This value can be changed
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through the use of the PORT_OFFSET variable. The PORT_OFFSET
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is optional and will be set to 61000 by fwknop if it is not specified
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-in /etc/fwknop/access.conf.
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+in %%PREFIX%%/etc/fwknop/access.conf.
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.TP
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.B MIN_TIME_DIFF: <seconds>
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Set the minimum number of seconds that must pass between successive
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